RFR: 8289538: Make G1BlockOffsetTablePart unaware of block sizes [v2]

[Thomas Schatzl]

> Hi all,
> 
>   can I have reviews for this change that makes `G1BlockOffsetTablePart` unaware of block sizes: as discussed in PR#9059/[JDK-8287555](https://bugs.openjdk.org/browse/JDK-8287555) this is a good idea to make `G1BlockOffsetTablePart` just for "dumb" retrieval of the BOT entries, which makes the code simpler, avoiding some calling back and forth between `HeapRegion` and `G1BlockOffsetTablePart`.
> 
> There is still the wart that `G1BlockOffsetTablePart::verify()` needs `block_size`, but since it's just verification I think this is fine. An alternative suggested by @albertnetymk is to remove that method completely.
> 
> Testing: local compilation, gha, some benchmark checking that card scans/ms does not degrade
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:

  Make block_start_reaching_into_card() const

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/9395/files
  - new: https://git.openjdk.org/jdk/pull/9395/files/c43b00e8..9e847fc0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9395&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9395&range=00-01

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9395.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9395/head:pull/9395

PR: https://git.openjdk.org/jdk/pull/9395